The invention relates to the cooling of gas turbine engine turbine blades, and particularly to the cooling of blade platforms.
A turbine assembly for a gas turbine engine generally includes a plurality of turbine blades mounted on a turbine disc so as to protrude radially therefrom. Each blade includes an aerofoil, which projects into the path of hot gases flowing axially through the turbine, and a circumferentially extending blade platform located at the radially inner base of the aerofoil. The turbine blades are closely spaced around the circumference of the rotor disc and the blade platforms meet to form a smooth annular surface.
Turbine blades are required to operate at high temperatures and turbine blade cooling is thus very important. It is known to cause air to flow through passages within the aerofoils of turbine blades, before expelling the air through orifices in the aerofoil surface. The internal air flow cools the blade by convection and the expelled air also forms a cooling film over the surface of the blade. This cools the aerofoil but does not result in significant cooling of the blade platforms.
According to the invention there is provided a turbine assembly including a plurality of turbine blades mounted on a rotatable support means so as to extend radially therefrom, wherein at least one turbine blade includes a blade platform spaced from the support means and wherein means are provided for allowing the passage of air from an internal region of the blade to a space located between the blade platform and the support means.
Preferably means are also provided for allowing the passage of air from the space into the blade.
The internal region of the blade may include one or more internal passageways for receiving cooling air, and means may be provided for allowing the passage of air from a first passageway to the space and for allowing the passage of air from the space to a second passageway. Preferably the blade includes an aerofoil portion located radially outwardly of the blade platform and the internal passageways extend into the aerofoil portion.
The assembly may further include means for allowing the passage of air from the space into an internal region of an adjacent blade.
Preferably the means for allowing the passage of air includes a plurality of orifices provided in a surface of the turbine blade.
The blade may include a root portion for mounting the blade on the rotatable support means and a shank portion extending between the root portion and the blade platform, and the orifices may be provided in the shank portion.
The turbine assembly may include a means for providing cooling air to the turbine blade via a passageway extending through its root portion.
An undersurface of the blade platform may be provided with a plurality of projections.
According to the invention there is further provided a gas turbine engine including a turbine assembly as defined in any of the preceding eight paragraphs.
According to the invention there is also provided a method of cooling a turbine assembly according to any of the above definitions, the method including the steps of passing air from an internal region of a turbine blade to the space, and passing air from the space into the internal region of the turbine blade or into an internal region of an adjacent turbine blade.
According to the invention there is further provided a turbine blade adapted for use in a turbine assembly according to any of the previous definitions.
According to the invention there is further provided a turbine blade for mounting on a rotatable support means so as to extend radially therefrom, the blade including a blade platform spaced from the support means in use and means for allowing air to pass from an internal region of the blade to a space located in use between the blade platform and the support means.
According to the invention there is further provided a turbine blade for mounting on a rotatable support means so as to extend radially therefrom, the turbine blade including a root portion for mounting the blade on the support means, a blade platform spaced from the root portion and a shank portion extending between the root portion and the blade platform, and wherein a surface of the shank portion is provided with a plurality of orifices for allowing the passage of air to and from an internal region of the blade.